(a)
Interpretation:
The catalyst, intermediate, and the rate-determining step if the rate law is
Concept introduction:
Reaction: Substances which are mutually involved each other in a chemical process and changed into different substances.
Mechanism of a reaction: The representation of step by step process involved in the chemical process is said to be mechanism of a
Rate determining step of a reaction: The speed or rate at which the overall the total reaction done and which is slowest step of the chemical reaction.
Catalyst: A substance or a compound which promotes the rate of a chemical reaction is said to be catalyst.
Rate of a reaction: It represents the speed at which a chemical reaction runs. How much concentration of reactants consumed and how much concentration of product formed in a unit of time is said to be
To identify the catalyst, intermediate, and the rate-determining step if the rate law is
(b)
Interpretation:
The given reaction is slow without the catalyst has to be explained.
Concept introduction:
Reaction: Substances which are mutually involved each other in a chemical process and changed into different substances.
Mechanism of a reaction: The representation of step by step process involved in the chemical process is said to be mechanism of a chemical reaction.
Rate determining step of a reaction: The speed or rate at which the overall the total reaction done and which is slowest step of the chemical reaction.
Catalyst: A substance or a compound which promotes the rate of a chemical reaction is said to be catalyst.
Rate of a reaction: It represents the speed at which a chemical reaction runs. How much concentration of reactants consumed and how much concentration of product formed in a unit of time is said to be rate of reaction.
To explain the given reaction is slow without the catalyst
(c)
Interpretation:
The types of catalysis have to be explained.
Concept introduction:
Reaction: Substances which are mutually involved each other in a chemical process and changed into different substances.
Mechanism of a reaction: The representation of step by step process involved in the chemical process is said to be mechanism of a chemical reaction.
Rate determining step of a reaction: The speed or rate at which the overall the total reaction done and which is slowest step of the chemical reaction.
Catalyst: A substance or a compound which promotes the rate of a chemical reaction is said to be catalyst.
Rate of a reaction: It represents the speed at which a chemical reaction runs. How much concentration of reactants consumed and how much concentration of product formed in a unit of time is said to be rate of reaction.
To explain the types of catalysis
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Chemistry: Atoms First
- The hydrolysis of the sugar sucrose to the sugars glucose and fructose, C12H22O11+H2OC6H12O6+C6H12O6 follows a first-order rate equation for the disappearance of sucrose: Rate =k[C12H22O11] (The products of the reaction, glucose and fructose, have the same molecular formulas but differ in the arrangement of the atoms in their molecules.) (a) In neutral solution, k=2.11011s1 at 27 C and 8.51011s1 at 37 C. Determine the activation energy, the frequency factor, and the rate constant for this equation at 47 C (assuming the kinetics remain consistent with the Arrhenius equation at this temperature). (b) When a solution of sucrose with an initial concentration of 0.150 M reaches equilibrium, the concentration of sucrose is 1.65107M . How long will it take the solution to reach equilibrium at 27 C in the absence of a catalyst? Because the concentration of sucrose at equilibrium is so low, assume that the reaction is irreversible. (c) Why does assuming that the reaction is irreversible simplify the calculation in pan (b)?arrow_forwardIn the presence of excess thiocyanate ion, SCN, the following reaction is first order in iron(III) ion, Fe3+; the rate constant is 1.27/s. Fe3+(aq)+SCN(aq)Fe(SCN)2+(aq) What is the half-life in seconds? How many seconds would be required for the initial concentration of Fe3+ to decrease to each of the following values: 25.0% left, 12.5% left, 6.25% left, 3.125% left? What is the relationship between these times and the half-life?arrow_forwardAs with any drug, aspirin (acetylsalicylic acid) must remain in the bloodstream long enough to be effective. Assume that the removal of aspirin from the bloodstream into the urine is a lirst-order reaction, with a half-life of about 3 hours. The instructions on an aspirin bottle say to take 1 or 2 tablets every 4 hours. If a person takes 2 aspirin tablets, how much aspirin remains in the bloodstream when it is time for the second dose? (A standard tablet contains 325 mg of aspirin.)arrow_forward
- (Section 11-5) A rule of thumb is that for a typical reaction, if concentrations are unchanged, a 10-K rise in temperature increases the reaction rate by two to four times. Use an average increase of three times to answer the questions below. (a) What is the approximate activation energy of a typical chemical reaction at 298 K? (b) If a catalyst increases a chemical reactions rate by providing a mechanism that has a lower activation energy, then what change do you expect a 10-K increase in temperature to make in the rate of a reaction whose uncatalyzed activation energy of 75 kJ/mol has been lowered to one half this value (at 298 K) by addition of a catalyst?arrow_forwardIn the presence of excess thiocyanate ion, SCN, the following reaction is first order in chromium(III) ion, Cr3; the rate constant is 2.0 106/s. Cr3+(aq)+SCN(aq)Cr(SCN)2+(aq) What is the half-life in hours? How many hours would be required for the initial concentration of Cr3 to decrease to each of the following values: 25.0% left, 12.5% left, 6.25% left, 3.125% left?arrow_forwardWhen enzymes are present at very low concentration, their effect on reaction rate can be described by first-order kinetics. Calculate by what factor the rate of an enzyme-catalyzed reaction changes when the enzyme concentration is changed from 1.5 107 M to 4.5 106 M.arrow_forward
- . explain the difference between elementary reactions and multistep reactions.arrow_forwardThe decomposition of azomethane, (CH3)2N2, to nitrogen and ethane gases is a first-order reaction, (CH3)2N2(g)N2(g)+C2H6(g). At a certain temperature, a 29-mg sample of azomethane is reduced to 12 mg in 1.4 s. (a) What is the rate constant k for the decomposition at that temperature? (b) What is the half-life of the decomposition? (c) How long will it take to decompose 78% of the azomethane?arrow_forwardThe decomposition of NO2(g) occurs by the following bimolecular elementary reaction: 2NO2(g)2NO(g)+O2(g) The rate constant at 273 K is 2.3 1012 L/mol s, and the activation energy is 111 kJ/mol. How long will it take for the concentration of NO2(g) to decrease from an initial partial pressure of 2.5 atm to 1.5 atm at 500. K? Assume ideal gas behavior.arrow_forward
- The label on a bottle of 3% (by volume) hydrogen peroxide, H2O2, purchased at a grocery store, states that the solution should be stored in a cool, dark place. H2O2decomposes slowly over time, and the rate of decomposition increases with an increase in temperature and in the presence of light. However, the rate of decomposition increases dramatically if a small amount of powdered MnO- is added to the solution. The decomposition products are H2O and O2. MnO2 is not consumed in the reaction. Write the equation for the decomposition of H2O2. What role does MnO2 play? In the chemistry lab, a student substituted a chunk of MnO2 for the powdered compound. The reaction rate was not appreciably increased. WTiat is one possible explanation for this observation? Is MnO2 part of the stoichiometry of the decomposition of H2O2?arrow_forwardWhen formic acid is heated, it decomposes to hydrogen and carbon dioxide in a first-order decay: HCOOH(g)CO2(g)+H2(g) The rate of reaction is monitored by measuring the total pressure in the reaction container. Time (s) Pressure (torr) 0 220 50 324 100 379 150 408 200 423 250 431 300 435 Calculate the rate constant and half-life in seconds for the reaction. At the start of the reaction (time = 0), only formic acid is present. (HINT: Find the partial pressure of formic acid using Dalton's law of partial pressure and the reaction stoichiometry to find PHCOOH at each time.)arrow_forwardThe acid-catalyzed iodination of acetone CH3COCH3(aq) + I2(aq) CH3COCH2I(aq) + HI(aq) is a common laboratory experiment used in general chemistry courses to teach the method of initial rates. The reaction is followed spectrophotometrically by the disappearance of the color of iodine in the solution. The following data (J. P. Birk and D. L Walters, Journal of Chemical Education, Vol. 69, p. 585, 1992) were collected at 23 C for this reaction. Determine the rate law for this reaction.arrow_forward
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